The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

CAUGHT in the act: nighttime activity in Lemur catta

Cathemerality is an activity pattern consisting of discrete periods of diurnal and nocturnal activity. Though uncommon within the vast majority of Primates, several Malagasy strepsirhines, such as Eulemur and Hapelemur, maintain cathemeral activity patterns. Interestingly, several researchers have reported at least some nighttime activity in Lemur catta, yet this species is regarded as "strictly diurnal." As part of a larger study of L. catta feeding ecology in dry/spiny forest at Tsimanampetsotsa National Park, Madagascar, I used camera traps to examine cathemeral behavior in L. catta. From September 2010 to April 2011, two camera traps were placed near each of two lemur groups' sleeping sites. A total of 1067 unique lemur photos resulted, and 451 of these photos were after dark. Using the number of nighttime photos as a proxy for activity levels, no significant differences were found between the two lemur groups. Nighttime lemur activity increased with cool nighttime mean monthly temperatures (R2=0.604, p=0.040). However, neither correlation nor linear regression could explain variation between nighttime activity and mean monthly day length, temperature maximum, rainfall (or phenological abundance), and nightly moon illumination. These data were unexpected given that increased nocturnal activity with cool nightly temperatures has not been previously reported. Furthermore, in other lemur species, increased nocturnality is coupled with increased moon illumination, yet no such association was found here. Though further research is required to fully understand the proximate factors of nocturnal activity in L. catta, this speciesshould be considered cathemeral, rather than strictly diurnal.

Grant Sponsors: National Science and Engineering Research Council of Canada, 296264; National Science Foundation, 1028708; and National Geographic Society, 8880-11.